Process for removing contaminant from a surface and composition useful therefor

ABSTRACT

Particulate and metal ion contamination is removed from a surface, such as a semiconductor wafer containing copper damascene or dual damascene features, employing a fluoride-free aqueous composition comprising a dicarboxylic acid and/or salt thereof; and a hydroxycarboxylic acid and/or salt thereof or amine group containing acid.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.09/893,968, filed Jun. 29, 2001 now U.S. Pat. No. 6,627,546.

TECHNICAL FIELD

The present invention relates to an acidic aqueous composition that isespecially useful for removing particulate and metallic contaminationfrom a surface. The present invention is especially useful for removingparticulate and metallic contaminants from structures such as those usedas interconnect structures in integrated circuit devices such assemiconductor wafers containing copper damascene and dual damascenefeatures. The structures treated according to the present inventioninclude those that have been previously planarized by chemicalmechanical polishing.

BACKGROUND OF THE INVENTION

On VLSI and ULSI semiconductor chips, Al and alloys of Al are used forconventional chip interconnect/wiring material. However, more recentlycopper and alloys of copper have been developed as chip interconnectmaterial. The use of copper and copper alloys results in improved deviceperformance when compared to Al and its alloys.

In the fabrication of semiconductor devices, the metallic interconnectmaterial or wiring such as the copper or its alloys is typicallyplanarized after deposition.

Polishing slurries used for this planarization are typically aqueoussuspensions comprised of a metal oxide abrasive (such as alumina),organic acids, surfactants, and a suitable oxidizing agent. This processis known as chemical-mechanical polishing (CMP). The oxidizing agentworks to enhance mechanical removal of material via a corrosion assistedprocess. Such oxidizing agents employed in commercially-available orproprietary slurries are typically inorganic metal salts such as FeNO₃,or KIO₃, and also hydrogen peroxide, present in significantconcentrations. Other chemicals added to slurries to improve dispersionor otherwise enhance performance often are organic acids (e.g. citricacid). Sodium, potassium, and iron salts and/or compounds are frequentlyused in slurry formulations, and significant amounts of these metal ionimpurities can remain on the wafer after polishing and post-polishcleaning.

Therefore, a tendency exists for various particulate contaminants toremain on the polished surface. The particulate materials are extremelydifficult to remove. This is particularly problematic since the removalmust not adversely affect the polished surface.

Furthermore, since the polishing slurries typically contain an oxidizingagent, an oxide layer usually is present on the copper due tooxidization of the copper during the CMP process. This layer mayadversely affect the electrical characteristics of the device, and ispreferably removed. In fact, this layer may also contribute to thecontamination.

Accordingly, a need exists for a post chemical mechanical polishingcleaning chemistry that removes metallic and particulate contamination.In addition, it is desired that the cleaning step remove any residualcopper oxides and/or other non-desirable surface films, leaving a barecopper surface.

The problems of developing such a cleaning is further exacerbated by theneed to minimize etching of the copper as well as avoiding increasedsurface roughness to any significant extent.

Moreover, compositions containing fluorides have been suggested.However, it has become desirable to provide fluoride-free compositionsdue to environmental considerations.

SUMMARY OF THE INVENTION

The present invention relates to an acidic aqueous solution that isespecially for cleaning metallic/metal ion contaminants and especiallymetal and non-metal oxide particles remaining at or in the surface of asemiconductor wafer following CMP.

The present invention is particularly useful for removing particulatecontaminants from copper. The present invention also removes anyresidual oxide layer found on the copper surface without etching orincreasing the surface roughness of the copper to any significantextent.

In particular, the present invention relates to a fluoride-free aqueouscomposition comprising about 0.005 to about 16% by weight of at leastone dicarboxylic acid, salt thereof or mixture thereof,

-   -   about 0.003 to about 4% by weight of at least one hydroxy        carboxylic acid, salt thereof or mixture thereof; or an amine        group-containing acid and the remainder being substantially        water, and    -   having a pH of about 1 to about 4.

A further aspect of the present invention is concerned with a processfor removing particulate contaminants from a copper surface after CMPplanarization. In particular, the process comprises contacting a coppersurface that has been planarized by CMP with one of the above-disclosedaqueous compositions.

A still further aspect of the present invention relates to a process forfabricating semiconductor integrated circuits. The process comprisesforming circuits on the surface of a semiconductor wafer byphotolithographic process wherein the circuits comprise copper or copperalloy; planarizing the surface by chemical mechanical polishing; andremoving particulate and metallic (e.g.—metal ion) contaminants from thesurface by contacting with one of the above-disclosed aqueouscompositions.

Still other objects and advantages of the present invention will becomereadily apparent by those skilled in the art from the following detaileddescription, wherein it is shown and described only the preferredembodiments of the invention, simply by way of illustration of the bestmode contemplated of carrying out the invention. As will be realized theinvention is capable of other and different embodiments, and its severaldetails are capable of modifications in various obvious respects,without departing from the invention. Accordingly, the description is tobe regarded as illustrative in nature and not as restrictive.

DESCRIPTION OF BEST AND VARIOUS MODES FOR CARRYING OUT INVENTION

A number of criteria must be considered to establish an acceptable wafercleaning process. In particular, the ideal cleaning process shouldreduce particulate and metallic contaminants on the wafer to the levelpresent before the polishing step. Also, the cleaning process andchemistry must be compatible with the materials exposed on the wafersurface after CMP. Furthermore, one should be able to perform thecleaning process safely using commercially available wafer orfabrication equipment. Moreover, it is desirable that the process berelatively inexpensive to implement. Furthermore, environmentalconsiderations make it desirable that the composition be fluoride-free.

The structures treated pursuant to the present invention are typicallysemiconductor devices having copper interconnects (lines, plugs, vias,global and local interconnects) imbedded into a low k dielectricmaterial such as silicon dioxide, which may also include a cappinglayer, such as silicon nitride as in low k dielectric/damascene and dualdamascene structures. The silicon dioxide is typically a high densityplasma deposited silicon dioxide or TEOS (tetraethylorthosilicate).

The copper interconnects typically use either tantalum, tantalumnitride, or titanium or titanium nitride as a barrier or liner materialbetween the copper and the dielectric. As such, the post-CMP cleaningsolution is meant to clean up to four or more different materials,copper, the liner material, the dielectric or capping layer, as well asthe wafer backside, which is generally a thin layer of oxidized silicon.All these types of materials are exposed on the surface of thesemiconductor device during post-CMP cleaning. Accordingly, the cleaningcomposition must not adversely effect any of these materials to anundesired degree while still effectively removing the contaminants. Thisplaces considerable constraints upon developing a suitable composition.

The copper is planarized after deposition by chemical mechanicalpolishing typically employing an aqueous slurry comprising an abrasiveand an oxidizing agent. Such compositions are well known and need not bedescribed in any detail herein. Examples of some chemical mechanicalpolishing slurries can be found in U.S. Pat. No. 5,527,423 and U.S. Pat.No. 5,693,239, and PCT publication WO 97/43087, disclosures of which areincorporated herein by reference.

The structure is then contacted with a fluoride-free aqueous compositionaccording to the present invention. The composition comprises at leastone dicarboxylic acid and/or salt thereof; and at least onehydroxycarboxylic acid and/or salt thereof; or an amine group containingacid.

Use of the term “fluoride-free” herein refers to at least substantiallyfluoride-free (e.g. containing no more than about 100 ppb of fluoride).Typical dicarboxylic acids include those having two to six carbon atoms,and include oxalic acid, malonic acid, succinic acid, glutaric acid,adipic acid, maleic acid and fumaric acid. The preferred acid is malonicacid. Suitable salts include the alkali metal, alkaline earth metal andammonium salts. Preferably, a mixture comprising malonic acid and oxalicacid is employed.

Examples of hydroxycarboxylic acids includes malic acid, tartaric acidand citric acid.

The preferred hydroxycarboxylic acid is citric acid. Suitable saltsinclude alkali metal, alkaline earth metal and ammonium salts.

A preferred derivative is ammonium citrate.

The amine-containing acid is preferably glycine.

In addition to water, preferably deionized water, the composition caninclude minor amounts (e.g. up to about 0.002% by weight of the activeportion) of a biocide. A typical biocide is Kathan. Kathan comprises:

-   -   1.2% 5-chloro-2-methyl-4-isothiazolin-3-one    -   0.4% 2-methyl-4-isothiazolin-3-one    -   1.1% MgCl₂    -   1.75% Mg(NO₃)₂    -   0.16% copper nitrate trihydrate    -   water 95.85%.

The dicarboxylic acid and/or salt is typically present in amounts ofabout 0.005 to about 16 weight %, more typically about 0.1 to about 3weight % and preferably about 0.3 to about 0.5 weight %. When thepreferred mixture of oxalic acid and malonic acid is used, each one istypically present in amounts of about 0.003 to about 8 weight %, moretypically about 0.05 to about 1.5 weight % and preferably about 0.1 toabout 0.3 weight %.

The hydroxycarboxylic acid is typically present in the composition atamounts of about 0.003% to about 8% by weight, more typically about 0.05to about 1.5 weight % and preferably about 0.1% to about 0.3% by weight.

When employed, the amino-group containing acid such as glycine istypically employed in amounts of about 0.003 to about 4% by weight, moretypically about 0.005 to about 1.5 weight % and preferably about 0.005to about 0.05% by weight.

In addition, the compositions of the present invention have a pH ofabout 1 to about 4 and preferably about 1 to about 3, a particularexample being about 2. The pH is typically measured using pH paper orsuitable pH reference electrode. It has been discovered according to thepresent invention that the pH is important in achieving objectives ofthe present invention. In particular, the compositions are capable ofremoving metallic and non-metallic particulate oxides, as well assilicon dioxide; metal ion contaminants such as K, Ca, Ti, Cr, Mn, Fe,Ni, Cu and Zn; various sulfur and chloride impurities adsorbed on thevarious surface materials present on the wafer. CuO is thermodynamicallyunstable within the pH range of the compositions of the presentinvention.

A further feature of the present invention is that the composition evenin concentrated form is relatively stable. For instance, concentrates ofthe composition comprising about 0.1 to about 16% by weight andpreferably about 6% to about 10% by weight of the dicarboxylic acid,about 0.05% to about 8% by weight, and preferably about 3% to about 5%by weight of the dihydroxy carboxylic acid or amino acid and theremainder being substantialy water can be provided and transported tothe end user, the user can then dilute it such as about a 19:1 dilutionby weight at the process tool for convenience and for economicalreasons.

The composition can be used in a double sided brush scrubber to cleanwhole wafers following a copper CMP polishing step. Moreover, such canbe used in a megasonic bath or spray tool cleaning apparatus, orcombination thereof.

The following non-limiting examples are presented to further illustratethe present invention.

EXAMPLE 1

A concentrate comprising about 160 grams of citric acid, about 80 gramsof malonic acid, about 160 grams of oxalic acid and about 10 grams ofKathon™ biocide with about 3590 grams of ultra-high purity (UHP) wateris prepared. The concentrate has pH of about 1.05 as measured using acalibrated antimony reference electrode or pH paper. The concentrate isthen diluted 19:1 (by weight) with UHP H₂O to formulate an aqueouscleaning mixture, containing about 0.2 weight % of citric acid, about0.1 weight % of malonic acid, about 0.2 weight % oxalic acid, about0.0125 weight % Kathon™ biocide and about 99.5 weight % of water.

Wafers having copper lines embedded into silicon dioxide and lines witha liner material are first subjected to CMP employing an aqueous slurrycomprising about 2% by weight alumina, about 3% by weight H₂O₂, with theremainder being water and minor additives. After the CMP, the wafers arecontacted with the above aqueous cleaning mixture.

EXAMPLE 2

A concentrate comprising about 200 grams of oxalic acid, about 80 gramsof malonic acid, about 200 grams of glycine with about 3510 grams ofultra-high purity (UHP) water is prepared. The concentrate has pH ofabout 2.15 as measured using a calibrated antimony reference electrodeor pH paper. The concentrate is then diluted 19:1 (by weight) with UHPH₂O to formulate an aqueous cleaning mixture containing about 0.25weight % of oxalic acid, about 0.1 weight % of malonic acid, about 0.25weight % glycine and about weight 99.4% of water.

Wafers having copper lines embedded into silicon dioxide and lines witha liner material are first subjected to CMP employing an aqueous slurrycomprising about 2% by weight alumina, about 3% by weight H₂O₂, with theremainder being water and minor additives. After the CMP, the wafers arecontacted with the above aqueous cleaning mixture.

EXAMPLE 3

In a series of cleaning experiments, a subset of the following threedifferent wafer types are employed to characterize the cleaningperformance.

-   -   a) oxidized silicon substrates, with the oxide formed by        plasma-enhanced chemical vapor deposition (PECVD) using        tetraethylorthosilicate (TEOS) precursor.    -   b) thermally oxidized silicon substrates (TOX).    -   c) silicon substrates covered with a thin film of TEOS oxide        upon which is deposited 250 Å of Tantalum by physical vapor        deposition (PVD) followed by 1 kÅ of PVD Cu.    -   d) Patterned wafer films consisting of etch trenches in TEOS,        followed by deposition of 250 Å of Tantalum by physical vapor        deposition (PVD) followed by 1 kÅ of PVD Cu and then 10 kÅ of        electroplated Cu.

These wafer types as detailed above are then pre-processed according toeither of three different approaches as typically done in post-CMP cleancharacterization work.

-   -   a) No slurry processing with the wafer type being subjected to        subsequent cleaning only.    -   b) The wafer type receiving only a dip in the CMP slurry and        then subsequently cleaned.    -   c) The wafer type receiving polishing on a production quality        CMP tool and then subsequently cleaned.

The preprocessed wafers as detailed above are then cleaned(post-processed) according to either of two different approaches astypically done in post-CMP clean characterization work.

-   -   a) cleaned using a double-sided brush scrubber    -   b) cleaned using the immersion technique in a megasonic bath.

The cleaned (post processed) wafers as detailed above are thencharacterized using accepted metrology tools as typically done inpost-CMP clean evaluation work including one or more of the following.

-   -   a) Particle performance using light scattering metrology        equipment    -   b) Elemental analysis using transmission X-ray fluorescence        (TXRF) equipment    -   c) Elemental analysis using Drop Scan Etching (DSE) of the        dissolved surface silicon dioxide coupled with inductively        coupled plasma mass spectrometry (ICP-MS).    -   d) Static etch rate for copper and silicon dioxide via sheet        resistance by 4-pt probe and oxide thickness via ellipsometry,        respectively    -   e) Dynamic etch rate for copper and silicon dioxide via sheet        resistance by 4-pt probe and oxide thickness via ellipsometry,        respectively    -   f) Surface roughness of copper and oxide via atomic force        microscopy (AFM).

EXAMPLE 4

In a separate experiment, blanket TEOS films are processed in order toquantify the particle-based and elemental-based cleaning performance ofthe use-concentration chemistry depicted in example 1. In all cases,TEOS films are first characterized by laser light scattering on a Tencor6420 and Tencor SP1, to determine the particle precount at >0.2 μm andat >0.16 μm, respectively. The wafers are either sent directly throughthe scrubber-based cleaner without any slurry or CMP exposure, with onlya slurry dip in either commercially available Cu or Ta slurry, orpolished on an integrated CMP tool with the same slurry set. As seen inTable 1, the Tencor 6420 measurement tool indicates that the wafersimproved their cleanliness in all cases. The slurry dip films arecleaned to the level of the wafer that is cleaned but without slurryexposure. The TEOS films which received CMP processing are alsosignificantly cleaner, but show slightly higher post counts, which maybe non-particulate defectivity introduced by the CMP process and thus,is not a clean chemistry issue.

TABLE 1 Light point defect counts, pre and post processing, using Tencor6420 (>0.2 μm) and Tencor SP1 (>0.16 μm) on wafers without slurryexposure, with a slurry dip and with actual CMP processing. Tencor SP1Tencor 6420 LPDs Pre Post Delta Pre Post Delta Slurry Dip Al2O3 based-Cu Slurry 290 53 −243 38 12 −26 SiO2 based -Ta Slurry  24 10  −14 10  3 −7 CMP Al2O3 based -Cu Slurry 348 452   104 98 43 −55 SiO2 based -TaSlurry 226 983   757 61 35 −26 No Slurry N/A 433 45 −388 174   9 −165 A subset of the processed TEOS films are subsequently analyzed forsurface elements on both wafer

-   -   topside and backside using a Rigaku Model 3276 Total X-ray        Fluorescence Spectroscopy tool at 3 measurement sites per wafer.        Table 2 displays the corresponding wafer average results and        detection limits by element. Note that the Cl and S levels are        high and may either reflect a water quality issue at the        experiment location or a genuine element issue. Metal element        levels (Fe, Ni, Cu, Zn) for films which are slurry exposed are        below 1 ell at/cm² in all cases.

TABLE 2 Elemental analysis via TXRF on wafers processed without slurryexposure, with a slurry dip and with actual CMP processing, includingsmooth backside analysis. (All data is 1e10 at/cm2). TXRF Fe Ni Cu Zn ClS Ca Slurry Dip Al2O3 based -Cu Slurry 9.9 6.5 1 3.4 818 175  5 SiO2based -Ta Slurry 9.6 6.3 2.2 1 1265 94 5 CMP Al2O3 based -Cu Slurry 8.84.2 5.2 1.3 685 10 5 SiO2 based -Ta Slurry 6.1 2.3 3.7 1 499 102  7.1 NoSlurry n/a 19.9 12.3 2.6 1 670 61 5 Cleaned Cu/Ta Slurries 5.9 3.4 2.2 1412 94 5 Upside (Smooth Side TXRF) Down Det Limit n/a 2 1 1 1 7.5 10 5

EXAMPLE 5

In a separate cleaning experiment, a single cassette containing 24wafers, each with a film stack of 1 kÅ PVD Cu/250 Å PVD Ta/TEOS/Si, ispolished on a commercially available polishing platform with a twoslurry process the first slurry is an alumina-based slurry for Curemoval while the second slurry is a silica-based slurry for Ta removal.The wafers are otherwise polished using traditional productionconsumables and process parameters to clear the metal from the TEOS. Thewafers are subsequently cleaned in a stand-alone, double-sided brushscrubber using the composition and dilution specified in Example 1. Eachwafer is characterized for post-CMP clean particles. Average postparticle counts (light point defects) as measured using a Tencor 6420with a detection threshold of about >0.2 μm is 8 adders with a standarddeviation of less than 4 adders showing both capability and stability ofperformance. Table 3 displays the corresponding data for each wafer. Thelow post-count magnitude reflects the excellent slurry and slurryby-product particulate cleaning capability of the clean chemistry.

TABLE 3 Light Point Defect Counts via Tencor 6420 Wafer # 1 2 3 4 5 6 78 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 LPD > 0.2 μm 15 16 8 73 12 7 5 5 15 6 3 8 9 10 6 5 3 4 7 8 11 9 10A 4 wafer subset of the processed TEOS films are subsequently analyzedfor surface elements on both topside and backside using a Rigaku Model3276 Total X-ray Fluorescence Spectroscopy tool at 3 measurement sitesper wafer. Table 4 displays the corresponding wafer average results anddetection limits by element.

TABLE 4 Elemental analysis via TXRF on 4 wafers (3 sites/wafer)processed without slurry exposure, with a slurry dip and with actual CMPprocessing, including backside analysis. (All data is 1e10 at/cm2) Fe NiCu Zn Cl S Ca Mean 6.25 18.8 5.4 0 761 14.8 130 Std. Dev. 3.25 3.1 3.2 0162 51.4 63.6 Det Limit 2 1 1 1 7.5 10 5 Note that the Cl and Ca levelsare high and may reflect either a water quality issue at the experimentlocation or a genuine element issue. Metal element levels (Fe, Ni, Cu,Zn) for these-slurry exposed films were below 2e11 at/cm2 in all cases.

EXAMPLE 6

In a separate experiment, the static etch rate (SER) and dynamic etchrate (DER) of the use concentration clean chemistry specified in Example1 is evaluated on Cu and TEOS films, the results are shown in Table 5.For the static etch test, full 8″ wafers are placed in quantities of theuse-concentration chemistry (19 parts DI to 1 part concentrate) for 20minutes, then subsequently rinsed with UHP DI and dried. For the dynamicetch test, wafers are run through a double-sided brush scrubber at theuse-concentration for 20 minutes, rinsed and dried. The pre- andpost-process thickness are determined for the Cu and TEOS films by 4-ptprobe and ellipsometry, respectively. A low, but finite value of theetch rate is shown in call cases. The low etch rate magnitude of Cuprevents surface corrosion, grain, grain boundary and grain triple pointand film interface attack. It also minimizes associated surfaceroughness. The low but finite TEOS etch rates help in removing a thinand potentially element contaminated layer of TEOS. The pH of thecomposition is sufficiently low to destabilize surface copper oxide, yetminimizes the direct attack of Cu metal, with the intent to yield asclean and smooth a Cu surface as possible.

TABLE 5 Etch Rate Data (Å/min) via 4-pt prove and ellipsometry Cu TEOSSER 4.5 3.0 DER 5.0 4.5The polished and cleaned wafers are characterized with respect tosurface finish using an atomic force microscope. Both blanket Cu andpatterned films are polished using a silica-based slurry which polishesboth Cu, Ta and TEOS blanket films at approximately the same rate. Theblanket Cu film is partially polished using the silica-based slurry,buffed using UHP and H₂O and immediately cleaned using the compositionat use-concentration in a double-sided brush scrubber. The wafers arethen transferred to a Thermomicroscopes model MS atomic forcemicroscope. Two locations on each wafer are measured. For the patternedfilms an 80 μm×80 μm bond pad is chosen. Within this bond pad the RMSaverage roughness over a 2 μm×2 μm square is determined. For the blanketfilms, a random location of two 2 μm×2 μm measurement sites is utilized.In both cases, very low RMS roughness is obtained, consistent with thelow static and dynamic etch rates measured in other experiments. Table 6displays the actual values determined. We note that these values arevery low, reflective of the low metal etch rate of the composition, andprovides for a smooth surface finish.

TABLE 6 RMS Roughness (Angstroms) via M5 AFM Blanket Patterned Site 15.61 16.0 Site 2 7.23 17.1

EXAMPLE 7

In a separate example, a blanket thermally oxidized (TOX) silicon waferis immersed in a megasonic tank filled with the composition from Example1 after dipping it into a custom slurry product which is based upon analumina abrasive and peroxide oxidizer system. The wafer is subsequentlyrinsed with UHP H₂O and dried. The TOX wafer is characterized using aDigital Nanoscope III atomic force microscope (AFM), Tencor Surfscanfull-wafer light-point-defect detector both pre- and post-processing.Particle adders are −77 at >0.2 μm via the Tencor Surfscan. Elementalanalysis is performed using TXRF and indicated low levels, below thedetection limits in almost all cases, with the exception of Fe, Ca andZn which were close to the detection limit as shown in Table 7. Thecleaning potential of the composition with respect to slurry abrasiveparticles and surface elemental contamination has been clearlyevidenced.

TABLE 7 TXRF results K Ca Ti Cr Mn Fe Ni Cu Zn Wafer 1 <10 6 <6 <1 <0.74.5 0.9 <0.6 1.9 Wafer 2 <10 8  8 <1 <0.9 6.4 0.8 <0.6 1.9

EXAMPLE 8

In a separate experiment, 25 blanket TEOS dummy wafers and 3 test TEOSwafers are processed in order to quantify the particle-based andelemental-based cleaning performance of the use-concentrationcomposition depicted in example 2. In all cases, test TEOS wafers arefirst characterized by laser light scattering on a Tencor 6420 todetermine the particle pre-count at >0.2 μm. The wafers are sentdirectly through the stand-alone double-sided scrubber-based cleaningtool without any slurry or CMP exposure. As seen in Table 8, the Tencor6420 measurement tool indicates that the wafers show low post-particlecounts in all cases.

Subsequent to the 28 TEOS films, test wafer are subjected to a slurrydip and subsequently sent through the stand-alone scrubber. Such filmsshow clean capability at the same level or better than those wafers thatare cleaned but did not have an initial slurry exposure as shown inTable 8.

TABLE 8 Light point defect counts, pre and post processing, using Tencor6420 (>0.2 μm) on wafers without slurry exposure and with a slurry.Tencor 6420 LPDs Pre Post Delta No Slurry Clean Only 71 66 −5 No SlurryClean Only 27 55 28 No Slurry Clean Only 77 58 −19  Slurry Dip SiO2based - Ta Slurry 35 41  6

A subset of the processed TEOS films are subsequently analyzed forsurface elements on topside using a Rigaku Model 3276 Total X-rayFluorescence Spectroscopy tool at 3 measurement sites per wafer. Table 9displays the corresponding wafer average results and detection limits byelement. Note that the Cl level is high and may reflect a water qualityissue at the experiment location or a genuine element issue. Metalelement levels (Fe, Ni, Cu) for films which are slurry exposed to slurryare below 1.0 ell at/cm² in all cases.

TABLE 9 Elemental analysis via TXRF on wafers processed without slurryexposure and with a slurry dip. (All data is 1e10 at/cm2). TXRF Fe Ni CuCl S Ca Slurry Dip SiO2 based -Ta Slurry 9.6 6.3 2.2 1265 94 5 No SlurryClean Only 5 16 4 742 10 60  Det. Limit 2 1 1 7.5 10 5

EXAMPLE 9

In a separate cleaning experiment, two cassettes containing 30 waferstotal, each wafer with the film stack of 1 kÅ PVD Cu/250 Å PVDTa/TEOS/Si, are polished on a commercially available polishing platformwith a Ta slurry process. The slurry is a silica-based slurry for Taremoval, but also has an appreciable Cu polish rate. The wafers areotherwise polished using traditional production consumables and processparameters to clear the metal from the TEOS. The wafers are subsequentlycleaned in a stand-alone double-sided brush scrubber using thecomposition and dilution specified in Example 2. Each wafer ischaracterized for post-CMP clean particles. Average post particle counts(light point defects) as measured using a Tencor 6420 with a detectionthreshold of at >0.2 μm was 25.8 adders with a standard deviation of26.6 adders showing both capability and stability of performance. Note,wafer 5 is removed from the analysis due to an observed misprocess. Itis quite conceivable that other wafers are affected similarly, but sincethey were not analyzed by TXRF, it was not detected. Table 10 displaysthe corresponding data for each wafer. The low post count magnitudereflects the slurry and slurry by-product particulate cleaningcapability and stability of the composition of the invention andassociated process.

TABLE 10 Light Point Defect Counts via Tencor 6420 Waf. #  1  2  3  4  5 6  7  8  9 10 11 12 13 14 15 LPD @ >0.2 um 11 15 16 109  30k 15 10  711  6 19 17 19 34 38 Waf # 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30LPD @ >0.2 μm 44 39 30 28 23 18 21 30 120   4  8 21  8 11  5A 2-wafer subset of the processed TEOS films are subsequently analyzedfor surface elements on wafer topside using a Rigaku Model 3276 TotalX-ray Fluorescence Spectroscopy tool at 3 measurement sites per wafer.Table 11 displays the corresponding wafer average results and detectionlimits by element.

TABLE 11 Elemental analysis via TXRF on 4 wafers (3 sites/wafer)processed without slurry exposure, with a slurry dip and with actual CMPprocessing, including backside analysis. (All data is 1e10 at/cm2) Fe NiCu Zn Cl S Ca Mean 5.92 14.3 3.2 1 754 21.7 61.9 Std. Dev. 3.7 3.0 1.9 1145 32.5 33.6 Det Limit 2 1 1 1 7.5 10 5Note that the Cl levels are again high and reflect either a waterquality issue at the experiment location or a genuine element issue.Metal element levels (Fe, Ni, Cu, Zn) for these slurry-exposed films arebelow 2 ell at/cm² in all cases and reflect the elemental cleaningcapability of the compositions of the present invention.

The foregoing description of the invention illustrates and describes thepresent invention. Additionally, the disclosure shows and describes onlythe preferred embodiments of the invention but, as mentioned above, itis to be understood that the invention is capable of use in variousother combinations, modifications, and environments and is capable ofchanges or modifications within the scope of the inventive concept asexpressed herein, commensurate with the above teachings and/or the skillor knowledge of the relevant art. The embodiments described hereinaboveare further intended to explain best modes known of practicing theinvention and to enable others skilled in the art to utilize theinvention in such, or other, embodiments and with the variousmodifications required by the particular applications or uses of theinvention. Accordingly, the description is not intended to limit theinvention to the form disclosed herein. Also, it is intended that theappended claims be construed to include alternative embodiments.

1. A fluoride-free aqueous composition for removing particulatecontaminants from a copper surface after CMP planarization withoutadversely affecting the copper surface which consists essentially ofabout 0.003 to about 8% by weight of malonic acid; about 0.003 to about8% by weight of oxalic acid; about 0.003 to about 4% by weight of citricacid; and the remainder being substantially water; and having a pH ofabout 1 to about
 4. 2. The composition of claim 1 comprising about 0.2%by weight of citric acid; about 0.1% by weight of malonic acid and about0.2% by weight of oxalic acid.
 3. The composition of claim 1 whichfurther comprises a biocide.
 4. The composition of claim 3 wherein theamount of said biocide is up to about 0.002% by weight.
 5. Thecomposition of claim 3 wherein the amount of said biocide is about0.00005% by weight.
 6. The composition of claim 1 wherein the pH is upto about
 2. 7. A fluoride-free aqueous composition for removingparticulate contaminants from a copper surface after CMP planarizationwithout adversely affecting the copper surface which consistsessentially of about 0.005 to about 16% by weight of at least onedicarboxylic acid, salt thereof or mixture thereof; about 0.003 to about4% by weight of glycine; and the remainder being substantially water;and having a pH of about 1 to about
 3. 8. The composition of claim 7wherein the dicarboxylic acid or salt thereof has two to six carbonatoms.
 9. The composition of claim 7 wherein the dicarboxylic acid isselected from the group consisting of oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid, maleic acid and fumaric acid.10. A fluoride-free aqueous composition for removing particulatecontaminants from a copper surface after CMP planarization withoutadversely affecting the copper surface which consists essentially ofabout 0.005 to about 16% by weight of at least one dicarboxylic acid,salt thereof or mixture thereof; about 0.003 to about 4% by weight of atleast one amine group containing acid, salt thereof or mixture thereof;and the remainder being substantially water; and having a pH of about 1to about 3; and wherein the dicarboxylic acid comprises a mixture ofmalonic acid and oxalic acid.
 11. The composition of claim 10 whereinsaid at least one amine group containing acid is glycine.
 12. Afluoride-free aqueous composition for removing particulate contaminantsfrom a copper surface after CMP planarization without adverselyaffecting the copper surface which consists essentially of about 0.003to about 8% by weight of malonic acid; about 0.003 to about 8% by weightof oxalic acid; about 0.003 to about 4% by weight of glycine; and theremainder being substantially water; and having a pH of about 1 to about4.
 13. The composition of claim 12 comprising about 0.25% by weight ofglycine; about 0.1% by weight of malonic acid and about 5% by weight ofoxalic acid.
 14. The composition of claim 12 which further comprises abiocide.
 15. The composition of claim 14 wherein the amount of saidbiocide is up to about 0.002% by weight.
 16. The composition of claim 14wherein the amount of said biocide is about 0.00005% by weight.
 17. Thecomposition of claim 12 wherein the pH is up to about 2.